First of all, thanks for the help in my recent "Condensation in the
House" thread recently. Turns out the tenants were drying their clothes
in that area but with no ventilation and little heating.

Anyway, new problem now. Just to reiterate, this is a mid-terraced house
built in 1874. The house next door is now undergoing renovation and our
tenant texted us last night to say that next-door's builder has found a
hole in the chimney between the two properties and that it's joint
responsibility to repair it.

I've not been to the house yet so I don't know where this hole is, ie,
ground floor/bedroom level or roof. However, what I do know is that
about 18 months or two years ago, our house failed it's 'Landlord's Gas
Safety Check' because smoke was coming out of the sides of the chimney
stack rather than the top of the chimney pots and the solution to that
problem was to install new (aluminium?) flue liners for each of our two
gas fires.

Admittedly, I'm well out of my depth here but to my simplistic mind the
current problem can't be too bad... can it? I mean, if there's a hole,
surely all it needs is to be bricked up and it can't be that big a deal
can it? I'll give you more detail when I know more.